1. Field of the Invention
The present invention relates to connection control for controlling logical and physical connections of data communication and, more particularly, to a connection control device, a connection control method, a recording medium which records a connection control program and a data communication system enabling more efficient communication on a line switching system.
2. Description of the Related Art
Among communication systems for a data communication network such as the internet, most commonly employed is the packet exchange system. On the other hand, for a user to use a data communication network, commonly done is connecting to a provider or the like based on the line switching system using telephone lines.
Line switching system, which is one of switching modes for use in data transmission, is a switching system in which between a transmission side DTE (Data Terminating Equipment) which transmits information and a reception side DTE, a physical communication path is set up for every communication to transmit and receive data. The communication path set up here allows no other user to use and accordingly, a communication charge is ordinarily fixed according to a time period of line use.
In recent years, frequent mode of use is using a data communication network such as the internet from a data terminating equipment by means of a portable communication device outdoors and even in this case, connection to the data communication network is made through a radio telephone line of the line switching system using a portable telephone, personal handyphone system (PHS) or the like.
For making a connection to a data communication network by using the line switching service of a mobile communication network, employed is a dial-up server for the relay to a packet exchange network which terminates connections made by line switching. The dial-up server is in some cases disposed within a mobile communication network.
For making a connection to the internet from a mobile communication terminal, it is a common practice to, after making a connection to a dial-up server using telephone services and establishing a link by means of the PPP(Point to Point Protocol; RFC 1661) which is a layer 2 protocol (data link protocol), use the TCP/IP (Transmission Control Protocol/Internet Protocol) which is a higher-order protocol.
As to connection/disconnection between a mobile communication terminal and a dial-up server, telephone connection and PPP link are established upon a request from a user using the mobile terminal device. PPP monitors a state of a line and when the line is disconnected while a link is being established, ends the link.
In such mobile communication, however, propagation environments are often unstable to cause line disconnection. In data communication and the like using a mobile communication terminal, therefore, a once established logical line link is in many cases released (disconnected) as a physical line is disconnected.
As described in the foregoing, conventional connection control devices have the following problems.
First problem is wasteful consumption of telephone line resources such as radio resource.
The reason is that in data communication employing the line switching system, as described above, connection of a telephone line is continued from a connection request until a disconnection request made by a user similarly to a case of voice communication, thereby exclusively using the line while no data is transmitted thereon.
Telephone line resources such as radio resources are shared by numbers of users and affect a capacity of the entire system, and lack of line resources causes a problem that a new connection can not be made by other users.
In addition, it is a common practice in the line switching system to fix charges of use according to a time period of line use and even a connection time when data is actually neither sent nor received is charged, which is uneconomical for users.
Second problem is that when a line is disconnected due to some reason or other during communication, data communication should be ended halfway to conduct all the procedures for connection all over again from the beginning, which is inefficient and laborious operation.
Thirdly, in mobile communication, line disconnection often happens as mentioned above and every time the line disconnection occurs, a PPP link ends. Then, when communication is to be made with the same connection destination again such as in a case where desired data communication is yet to be completed, a user needs to make a connection request again to establish a PPP link.
Also in communication using the TCP such as the internet, when an interruption occurs, a TCP connection is released, so that data communication should be made over again starting with a connection and set-up of the connection.
An object of the present invention is to make efficient use of communication resources in data communication employing line switching, as well as providing environments convenient for users and efficient data communication.
According to the first aspect of the invention, a connection control device for controlling data communication involving set-up of a connection
provided on both sides of a communication source and a communication destination to control connection states of both sides in cooperation with a communication partner, each the device controlling communication between a data terminating equipment and a data circuit-terminating equipment on the side the device is disposed, comprising:
connection holding means for holding the state of an established connection after a disconnection of a physical line, and
communication resuming means for resuming communication by the connection held after a re-connection of a physical line.
In the preferred construction, wherein the state of a connection with a communication partner has three kinds of:
a release state indicative of a state where a physical line is disconnected and a connection is released,
a communication state indicative of a state where a physical line is connected and a connection is established, and
a wait state indicative of a state where a physical line is disconnected while holding a connection, and which further comprises
control means for processing a transition of the connection states.
In another preferred construction, the connection control device further comprises a control message communication means for transmitting and receiving information of a communication partner and information of a transition of the connection states to and from the communication partner as a control message, wherein
when receiving an instruction of a kind designated for controlling a connection of communication from the data terminating equipment, the control message communication means transmits the control message indicative of information of the instruction in question to the communication partner prior to execution of the instruction.
In another preferred construction, the connection control device further comprises information storage means for storing information of a communication partner and information of a connection with the communication partner, wherein
every time a new connection is established, the information storage means stores information of a communication partner having the connection in question and information of the connection in question.
In another preferred construction, when at the communication state, a physical line is disconnected without receiving a notification of a communication disconnection by the control message from a communication partner,
information stored in the information storage means is held as it is to make a transition to the wait state without executing processing of communication end by a disconnection of a physical line with respect to the data terminating equipment.
In another preferred construction, the connection control device further comprises a timer for determining a lapse of a fixed time, wherein
when no transmission and reception of communication data lasts longer than a fixed time in succession to and from a communication partner to which a physical line is connected, the physical line with the communication partner is disconnected and information stored in the information storage means is held as it is to make a transition to the wait state without executing processing of communication end by a disconnection of a physical line with respect to the data terminating equipment.
In another preferred construction, when at the wait state, transmission data to be sent to a waiting communication partner is received from the data terminating equipment,
a physical line with the communication partner is again connected to transmit the transmission data through a waiting connection stored in the information storage means, thereby making a transition to the communication state.
In another preferred construction, when at the wait state, a connection of a physical line is received from a waiting communication partner to receive data transmitted from the communication partner,
communication by a waiting connection stored in the information storage means is resumed to make a transition to the communication state.
In another preferred construction, when at the wait state, the control message communication means receives a control message notifying communication end from the communication partner,
information of a waiting connection stored in the information storage means is abandoned to make a transition to the release state.
In another preferred construction, the connection control device further comprises a timer for determining a lapse of a fixed time, wherein
when at the wait state, no communication with a waiting communication partner lasts longer than a fixed time before resumption,
information of a waiting connection stored in the information storage means is abandoned to make a transition to the release state.
In another preferred construction, the device is connected to a plurality of data circuit-terminating equipment and further comprises
server processing means for processing communication of a plurality of lines and a plurality of connections, and
management table storage means for centrally storing and managing information of a communication partner and information of a connection with the communication partner with respect to all the connections,
the server processing means includes
means for releasing resources of the data circuit-terminating equipment related to the communication in question at a transition to the wait state, and
means for referring to the management table storage means to search for the data circuit-terminating equipment not in use, thereby
conducting connection control for each of the plurality of connections.
In another preferred construction, when receiving a control message of a restoration request from a communication partner having a waiting connection, the server processing means
searches the management table storage means for information of the connection of the communication partner and resumes communication by the searched connection.
In another preferred construction, the device is internally provided with a function of the data circuit-terminating equipment.
In another preferred construction, the device is integrated with the data terminating equipment into one unit.
In another preferred construction, the device is a separate unit from the data terminating equipment and the data circuit-terminating equipment.
In another preferred construction, the device controls radio data communication.
According to the second aspect of the invention, a connection controlling method of controlling data communication involving set-up of a connection, wherein
on both sides of a communication source and a communication destination for controlling connection states of both sides in cooperation with a communication partner, communication is controlled between a data terminating equipment and a data circuit-terminating equipment on each side, and the method comprises the steps of:
connection holding of holding the state of an established connection after a disconnection of a physical line, and
communication resuming of resuming communication by the connection held after a re-connection of a physical line.
In the preferred construction, the state of a connection with a communication partner has three kinds of:
a release state indicative of a state where a physical line is disconnected and a connection is released,
a communication state indicative of a state where a physical line is connected and a connection is established, and
a wait state indicative of a state where a physical line is disconnected while holding a connection, and which further comprises
the control step of processing a transition of the connection states.
In another preferred construction, the connection controlling method further comprising the control message communication step of transmitting and receiving information of a communication partner and information of a transition of the connection states to and from the communication partner as a control message, wherein
when receiving an instruction of a kind designated for controlling a connection of communication from the data terminating equipment, at the control message communication step, the control message indicative of information of the instruction in question is transmitted to the communication partner prior to execution of the instruction.
In another preferred construction, the connection controlling method further comprising the information storing step of storing information of a communication partner and information of a connection with the communication partner, wherein
every time a new connection is established, information of a communication partner having the connection in question and information of the connection in question are stored at the information storing step.
In another preferred construction, when at the communication state, a physical line is disconnected without receiving a notification of a communication disconnection by the control message from a communication partner,
information stored at the information storing step is held as it is to make a transition to the wait state without executing processing of communication end by a disconnection of a physical line with respect to the data terminating equipment.
In another preferred construction, the connection controlling method further comprising a timer for determining a lapse of a fixed time, wherein when no transmission and reception of communication data lasts longer than a fixed time in succession to and from a communication partner to which a physical line is connected, the physical line with the communication partner is disconnected and information stored at the information storing step is held as it is to make a transition to the wait state without executing processing of communication end by a disconnection of a physical line with respect to the data terminating equipment.
In another preferred construction, when at the wait state, transmission data to be sent to a waiting communication partner is received from the data terminating equipment,
a physical line with the communication partner is again connected to transmit the transmission data through a waiting connection stored at the information storing step, thereby making a transition to the communication state.
In another preferred construction, when at the wait state, a connection of a physical line is received from a waiting communication partner to receive data transmitted from the communication partner,
communication by a waiting connection stored at the information storing step is resumed to make a transition to the communication state.
In another preferred construction, when at the wait state, the control message communication step receives a control message notifying communication end from the communication partner,
information of a waiting connection stored at the information storing step is abandoned to make a transition to the release state.
In another preferred construction, the connection controlling method further comprising a timer for determining a lapse of a fixed time, wherein
when at the wait state, no communication with a waiting communication partner lasts longer than a fixed time before resumption,
information of a waiting connection stored at the information storing step is abandoned to make a transition to the release state.
In another preferred construction, with a plurality of data circuit-terminating equipment connected, the method further comprises the steps of:
server processing of processing communication of a plurality of lines and a plurality of connections, and
management table storing of centrally storing and managing information of a communication partner and information of a connection with the communication partner with respect to all the connections,
the server processing step including the steps of:
releasing resources of the data circuit-terminating equipment related to the communication in question at a transition to the wait state, and
referring to the management table storage step to search for the data circuit-terminating equipment not in use, thereby
conducting connection control for each of the plurality of connections.
In another preferred construction, when receiving a control message of a restoration request from a communication partner having a waiting connection, the server processing step
searches for information of the connection of the communication partner at the management table storage step and resumes communication by the searched connection.
According to the third aspect of the invention, a computer readable memory storing a connection control program for controlling data communication involving set-up of a connection,
the computer readable memory being provided on both sides of a communication source and a communication destination for controlling connection states of both sides in cooperation with a communication partner and each the connection control program controlling communication between a data terminating equipment and a data circuit-terminating equipment on each side, wherein the connection control program comprises the steps of:
connection holding of holding the state of an established connection after a disconnection of a physical line, and
communication resuming of resuming communication by the connection held after a re-connection of a physical line.
According to another aspect of the invention, a data communication system for conducting data communication involving set-up of a connection, wherein
communication control devices are disposed on both sides of a communication source and a communication destination for controlling connection states of both sides in cooperation with a communication partner, each controlling communication between a data terminating equipment and a data circuit-terminating equipment on each side, and
the connection control device comprises:
connection holding means for holding the state of an established connection after a disconnection of a physical line, and
communication resuming means for resuming communication by the connection held after a re-connection of a physical line.
In the preferred construction, the state of a connection with a communication partner has three kinds of:
a release state indicative of a state where a physical line is disconnected and a connection is released,
a communication state indicative of a state where a physical line is connected and a connection is established, and
a wait state indicative of a state where a physical line is disconnected while holding a connection, and wherein the connection control device further comprises control means for processing a transition of the connection states.
In another preferred construction, the connection control device further comprises
control message communication means for transmitting and receiving information of a communication partner and information of a transition of the connection states to and from the communication partner as a control message,
the control message communication means, when receiving an instruction of a kind designated for controlling a connection of communication from the data terminating equipment, transmitting the control message indicative of information of the instruction in question to the communication partner prior to execution of the instruction.
In another preferred construction, the connection control device further comprises
information storage means for storing information of a communication partner and information of a connection with the communication partner, the information storage means, every time a new connection is established, storing information of a communication partner having the connection in question and information of the connection in question.
In another preferred construction, the connection control device,
when at the communication state, a physical line is disconnected without receiving a notification of a communication disconnection by the control message from a communication partner,
holds information stored in the information storage means as it is to make a transition to the wait state without executing processing of communication end by a disconnection of a physical line with respect to the data terminating equipment.
In another preferred construction, the connection control device further comprises
a timer for determining a lapse of a fixed time, and wherein the connection control device, when no transmission and reception of communication data lasts longer than a fixed time in succession to and from a communication partner to which a physical line is connected, disconnects the physical line with the communication partner and holds information stored in the information storage means as it is to make a transition to the wait state without executing processing of communication end by a disconnection of a physical line with respect to the data terminating equipment.
In another preferred construction, when at the wait state, receiving transmission data to be transmitted to a waiting communication partner from the data terminating equipment,
the connection control device again connects a physical line with the communication partner and transmits the transmission data through a waiting connection stored in the information storage means to make a transition to the communication state.
In another preferred construction, when at the wait state, receiving a connection of a physical line from a waiting communication partner to receive data transmitted from the communication partner,
the connection control device resumes communication by a waiting connection stored in the information storage means to make a transition to the communication state.
In another preferred construction, when at the wait state, the control message communication means receives a control message notifying communication end from the communication partner,
the connection control device abandons information of a waiting connection stored in the information storage means to make a transition to the release state.
In another preferred construction, the connection control device further comprises a timer for determining a lapse of a fixed time, and wherein
the connection control device, when at the wait state, no communication with a waiting communication partner lasts longer than a fixed time before resumption, abandons information of a waiting connection stored in the information storage means to make a transition to the release state.
In another preferred construction, the connection control device is connected to a plurality of data circuit-terminating equipment and further comprises:
server processing means for processing communication of a plurality of lines and a plurality of connections, and
management table storage means for centrally storing and managing information of a communication partner and information of a connection with the communication partner with respect to all the connections,
the server processing means including:
means for releasing resources of the data circuit-terminating equipment related to the communication in question at a transition to the wait state, and
means for referring to the management table storage means to search for the data circuit-terminating equipment not in use, thereby
conducting connection control for each of the plurality of connections.
In another preferred construction, when receiving a control message of a restoration request from a communication partner having a waiting connection, the server processing means
searches the management table storage means for information of the connection of the communication partner and resumes communication by the searched connection.
In another preferred construction, the system controls radio data communication.
Other objects, features and advantages of the present invention will become clear from the detailed description given herebelow.